Eddy-current ring construction for electrical machines



EDDY-CURRENT RING CONSTRUCTION FOR ELECTRICAL MACHINES Filed Se t; 13. 1950 June 9, 1953 n.1, JAESCHKE 2 Sheets-Sheet 1 June 9, 1953 R. JAESCHKE 2,641,722

EDDY-CURRENT RING CONSTRUCTION FOR ELECTRICAL MACHINES Filed Sept. 1:5, 1950 2 Sheets-Sheet 2 Patented June 9, 1953 EDDY-CURRENT RING CONSTRUCTION FOR ELECTRICAL MACHINES Ralph L. Jaeschke, Kenosha, Wis., assignor to Dynamatic Corporation, Kenosha, Wis., a corporation of Delaware Application September 13, 1950, Serial No. 184,599

9 Claims. (01. 310-105) This invention relates to eddy-current ring constructions, and more particularly to such constructions for electrical machines which are subject to heating such as eddy-current clutches, slip couplings, brakes and the like.

The invention is an improvement upon the construction shown in my United States patent application Serial No. 138,646, filed January 14, 1950, for Dynamoelectric Apparatus, eventuated as U. S. Patent 2,594,931, dated April 29, 1952.

Among the several objects of the invention may be noted the provision of a slotted, segmental eddy-current ring or drum having supporting webs between the drum hub and the drum segments of such shapes and relationships to the slots that strains due to heating have minimum efiect on the circularity and diameter of the drum and whereby high stresses are avoided. Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which several of Various possible embodiments of the invention are illustrated,

ble material such as soft iron or steel. As is known, drums of this type operate in association with a polar field member adjacent to the periphery of drum, the poles facing the drum across a small magnetic gap. The field member is attached either to the driving or driven member of the clutch. The field member is not shown in the drawings because various types for the purpose are well-known. An exemplary gap is indicated at dash lines 2. .Thus if the drum were connected to the driving member of the clutch, the field member would be connected to its driven member, or vice versa. Relative motion between the drum and the field member causes polar flux to sweep the magnetic material of the drum and to induce eddy currents which produce the desired reactive magnetic coupling between the drum and the field member. A typical field member is shown in Patent 2,470,596, which also shows a prior art form of eddy-current drum including known copper end rings which are designated l I in the present construction. Upon heating of the ring or drum during operation, some heat-dissipating means is often required. Under such conditions it is desirable to maintain the surface of the drum under varying temperature conditions circular and at as constant a diameter as possible, so that the magnetic gap 2 is accurately maintained. For example,

Fig. 1 is an end elevation of an eddy-current the usual gap between the field and the drum is ring or inductor drum showing one form of the of the order of .020 inch across, which does not inventi n; allow much range for distortion or expansion Fi 2 i cro cti n t ken n lin 2-2 of without gap trouble. In order to provide for the Fi 1; above-mentioned substantially constant circu- Fig 3 is a, development of 3, portion of the exlarity and diameter 0f the drum surface, it iS terior surface of the drum as viewed on line known 30 S101? it angularly obliquely (includ- 3 3 of i 1; ing the copper end rings H) as shown at Fi 4 i vi i il t Fig, 1 showing an numerals l, in order to divide it into segments 9. lternati mb diment of the in ention; In order to connect the segments 9 with the hub i 5 i a cross ti t k on li 5 5 I, spokes are provided in the form of webs l3. of Fig. 4; and Between the webs l3 are provided accordion- Fig. 6 is a plan view of one connecting plate folded heat-conducting units [5. The outer folds used in the form of the invention shown in Fig. ll of these units are heat bonded to the insides 4, drawn on a much reduced scale. of the segments 9 as by soldering, brazing or the Similar reference characters indicate correke. e te of the units, for D y spending parts throughout the several views of be copper or other suitable heat-conductive the drawings. flexible strip material. The inner folds I9 of Referring now more particularly to Fig. 1-, these units are not bonded to the hub I. Thus there is shown an eddy-current ring or drum for While the heat-dissipating units [5, being heat use in an eddy-current clutch or coupling. This bonded to the segments 9 may follow any movedrum comprises a hub I having bolting lugs 3 ments of the latter any resulting movements of for attachment either to the driving or driven the units [5 are independent of the hub I. member of the clutch. Numeral 5 shows in gen- After the webs l3 have been assembled beeral the outer eddy-current portion of the drum, tween drum 5 and hub I and welded, heat bondwhich is cylindric and composed of a magnetiza- 55 ing is generally carried out by brazing or soldering which is carried out by preassembling the units I between the drum 5 and the hub I (before slotting the drum). The solder, if any is used, is pre-inserted. Then the drum is heated to heat bonding temperature without applying heat to the hub. The temperature is so high during this formative heat bonding step that precautions must be taken against the development of excessive stresses at the junctures between the webs I3 and the drum 5, as will appear below. Finally the drum is slotted.

Thus an important feature of the invention is the improved character of the connections between the segments 9 and the hub I. These consist of the webs I3, each of which is composed of a generally U-shaped heavy steel plate having a radial space or slot 23. Beneath the space is a base portion 25 and on its sides are legs 21, which are axially aligned and axially spaced. The legs end in extensions 29, the web as a whole being exteriorly of generally hourglass shape, as shown in Fig. 2. In end view the webs are waveshaped, like an S (Fig. 1). Each web is notched at opposite corners as shown at 3| and 33, respectively, for engagement with shoulders 35 and 31, respectively, in the rim segments 9 and in the hub I.

The webs are located at the angular slots 1 in such a way that opposite extensions 29 respectively engage adjacent corners of the segments 9, at which points they are welded. The base 25 of each web is welded to the huh I. Each slot 23 in a web straddles the adjacent slot 1 between segments 9.

In construction the inductor rim is made up solid (including the rings II and before insertion of the slots 1) and after centering the hub the webs I3 are welded into position between the rim and the hub, the final exterior machining being provided at this time. Then the angular slots 1 may be gashed into the rim of the invention at points crossing the slots 23 in the webs. The units I5 are then heat bonded to the segments 9. Or, the units I5 may be heat bonded to the rim before gashing, the gashing being the final step. In any event, the heat bonding of the units I5 to the-segments 9 is accomplished by highly heating the rim only, to a temperature higher than even the subsequent operating temperature. Herein this heat bonding temperature is called the formative temperature. This high formative temperature considerably expands the rim (including peripheral elongation of the segments 9) and is the reason for which the webs I3 are made s-shaped instead of fiat. otherwise be high stresses at the rim and web junctures. The formative temperature is also the reason for which the extensions 29 are employed. These provide long welds under the rim, so that ample strength is provided at these points under the formative temperature.

Under operating conditions the temperature of the rim is also higher than that of the hub I but not as high as during the above-mentioned formative heating. Under these conditions the invention results in little radial expansion of the rotor as a whole, the heated segments 9 expanding primarily peripherally but being resiliently anchored at the slots 1, so as to maintain circularity and a substantially constant diameter.

Hence the small gap 2 is substantially accurately maintained under operating temperatures.

It will be observed that the peripheral elongation of the segments 9 upon heating, which mini- The S-shapes relieve that wouldmizes radial expansion of the rim, results in opposite movements of the corners of the segments 9, as indicated by the arrows in Fig. 3. These opposite movements are individually transferred to the adjacent legs 21 of the U-shaped webs I3. Thus while the long extensions 29 provide ample strength against shearing stresses at the rim welds, the slots 23 and the hourglass shapes of the webs I3 allow opposite bendings in the narrow portions of the legs 21. Thus sufiiciently rigid driving spokes are provided which are nevertheless flexible enough to prevent the formation of the damaging stresses, either during the formative heating of the rim during application of the units I5, or during the heating of the rim under operating conditions. The result is an inductor drum which is easy and economical to make and which, when finished and operating, has an extremely stable outside diameter. This stability is due to channeling most of the expansive movements of the rim into the peripheral direction, allowing for compensating relative movements between segments 9 at the slots 1. The compensating peripheral movements are absorbed by opposite movements of the opposite legs 21 of the webs I3 in such a manner as to build up only manageable (not excessive) bending stresses therein. Thus S-forms of the webs I3, their hourglass exterior shapes, and their internal U-shapes are each significant in a certain respect.

The principles of the invention are carried out in a slightly different form in Figs. 4 and 5. Stippling is employed in Fig. 4 only to distinguish in the drawing a certain part offset from an identical part, which in the absence of such stippling might be confusing. This is the only significance of the stippling.

In this form of the invention the hub is shown at 39 with its attachment lugs M. The rim or eddy-current ring is shown generally at 43 with its copper rings 45. In this case the rim is separated into three segments 41 by angular slots 49. The connections between the segments 41 and the hub 39 are made by means of identical annular side plates, one of which in Fig. 4, as stated above, is stippled (the forward one) and the other of which (the rearward one) is unstippled. The form of each is shown in Fig. 6. The forward plate is numbered 5I and the rearward plate is numbered 53. These annular side plates are relatively angularly positioned. Each consists of an inner ring 55 (welded against a shoulder 51 of the hub) and three T-shaped leaves 59 (welded to a shoulder 6| of the rim 43). The leaves are spaced from the ends of the segments 41, the plate 53 being offset with respect to the plate 5I (as indicated in Fig. 4). The offset is the amount of the offset of the ends of the angular slots 49. Thus each segment 41 is held at approximately mid point by a T-shaped leaf 59 extending from the hub 39.

Interdigitated between the leaves 59 and extending from the ring 55 are outwardly extending webs 63 of hourglass shape. Each web 63 has a space or slot 65 flanked by legs 61, each of which has an extension 13. The legs are joined by a base 69. An additional slot H is employed in each leg 61. The extensions 13 are welded on adjacent rim segments 41, the slots 65 straddling the angular slots 49 between segments.

The functioning of the Figs. 4-6 form of the invention is similar to that already described in that the extensions 13 form means for long individual welds with adjacent segments 41, while the slots 65 and hourglass shapes allow for compensating relative peripheral movements between the ends of the segments 41. Upon heating, adjacent legs 61 may distort toward one another as allowed by the slots 65 and H.

In this Figs. 4-6 form of the invention the heat-dissipating member is constituted by a single unit of accordion-folded strip having outer folds '17 heat bonded to the insides of the rim segments 41, the inner folds 19 being free of the hub. The spaces between ring members 5'! allow axial flow of air across the heat-dissipating strip 15. It will be noted that in this form of the invention the heat-dissipating strip can be made in a single length, instead of in several units, as in Fig. 1.

In connection with the Figs. 4-6 form of the invention, it will be understood that if desired the central supports at the'segments such as at 59 may be omitted if the rim segments are short. For example, if a greater number of segments were used, such as for example six, instead of the three shown in Fig. 4, then additional U- shaped webs such as 63 might be used at the points where the leaves 56 now appear, without use of the T-shaped leaves 59. Also, there are generally axially aligned, axially spaced legs at the slots or slits 49 in the drum.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. An eddy-current ring construction for electrical machines comprising a hub, a spaced surrounding segmental drum having slots determining its segments, and web members joining the hub and the drum, the general extension of each web member being axial but being of shaped contour, each web member comprising a U-shape in outline to provide axially spaced legs connecting the hub and adjacent segments respectively and to provide an intermediate space therein spanning a slot between adjacent segments. 1

2. An eddy-current ring construction for electrical machines comprising a hub, a spaced surrounding segmental drum having slots oblique to its axis and determining its segments, web members joining the hub and the drum, the general plane of each of which web members is axial but being of S-shaped contour, each web member comprising a U-shape in outline to provide axially spaced legs connecting the hub and adjacent segments respectively and to provide an intermediate space therein spanning a slot between adjacent segments, the exterior of each U-shape being of hourglass form to provide extended connections between the respective legs and said adjacent segments, and accordionfolded heat-dissipating units having their outer folds heat bonded to the segments and their inner folds unbonded with respect to the hub.

3. An eddy-current ring construction for electrical machines comprising a hub, a spaced surrounding segmental drum having oblique slots providing its segments, and circular end plate members fastened to the hub and the drum, each plate member comprising a number of radially extending web portions, each web portion having a U-shape to provide legs connecting the hub and adjacent segments respectively and to provide an intermediate space therein spanning a slot between adjacent segments, the legs on the respective end plates being offset to provide generally axially aligned portions at the slots in the drum, the exterior of each U-shape being of hourglass form to provide extended connections between the respective legs and said adjacent segments, said legs having additional radial openmgs.

4. In an electrical machine, a rotary eddy-current ring member, the member comprising a hub and a coaxial drum, with drum-supporting members fastened to the hub and the drum, the drumsupporting members being substantially spaced apart and each having leg portions separated by a space and the drum being segmented along slots extending entirely across the drum and between the spaced leg portions of the drum-supporting members so as to form individual drum segments, said spaces, with said leg portions, forming arching connections between said supporting members and portions of the segments on opposite sides of the slots, whereby said leg portions may move relatively freely with respect to one another in response to any relative movements of the ends of the segments adjacent the slots.

5. Apparatus as set forth in claim 4 further including a plurality of flexible non-supporting cooling fins located between the spaced drumsupporting members and engaging the drum.

6. Apparatus as set forth in claim 4 wherein th drum-supporting members comprise generally U-shaped web portions forming spaced legs, the legs extending radial-1y and being fastened at their ends to the drum.

7. Apparatus as set forth in claim 6 wherein the legs formed by the U-shaped webs are narrow in the center and more extensive at their ends where fastened to the drum, the extensive end portions being welded to the drum and the narrow central portions facilitating bending of the legs.

8. Apparatus as set forth in claim 7 wherein each drum-supporting member is a U-shaped web axially disposed and of wavy contour as viewed from the ends of the drum.

9. In an electrical machine, a rotary member subjected to peripheral heating, the member comprising a hub and a coaxial drum with drumsupporting members fastened to the hub and the drum, the drum-supporting members being substantially spaced apart, the drum having slits extending across it to separate it into segments, the drum-supporting members having pairs of legs extending from fastening means on the hub to aligned separate fastenings on the drum, there being an angle between the slits and the alignment of the fastenings to the drum, each pair of spaced fastenings on the drum being on opposite sides of a respective slit.

RALPH L. JAESCHKE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,043,047 Goldsmidt Oct. 29, 1912 1,834,774 Fischer Dec. 1, 1931 2,452,820 Winther Nov. 2, 1948 2,490,789 Ellis Dec, 13, 1949 

